A railroad car air compressor unit of the prior art is explained in greater detail with reference to FIGS. 2a, 2b, and 2c, which illustrate a side elevational view, a top plan view, and a schematic flow diagram, respectively, of a motor-compressor unit in accordance with the prior art. As shown, a railroad car air compressor unit 1 is suspended underneath the floor 2 of the railroad car and includes an electric motor 3, a compressor 4, a dust suction filter 5, a suction muffler 6, and a base frame 30 which supports and carries the motor, compressor, etc., and four suspension pieces 31 which suspend the base frame 30. The electric motor 3 is located and fixed on one side of the base frame 30 by a plurality of base support members 32. The compressor 4 is located and fixed on the other side of the base frame 30 by another plurality of base support members 32. The rotating shaft 13 of the electric motor 3 and the crank shaft 16 of the compressor 4 are connected via coupling member 17. The outside of this coupling member 17 is covered by the protective cover 33 which is made of a metal mesh which can readily dissipate the heat and which is fixed in a suitable manner to the base frame 30 for safety purposes.
The suction dust filter 5 and the suction muffler 6 are located on one of the sides of the electric motor 3 as a sinlge piece unit, while the terminal box 34 and inspection hatch 35 are located on the other side of the motor. In this type of construction, the air for the compressor 4 comes through the suction dust filter 5 and the suction muffler 6 is divided into the suction inlets 37 of two low-pressure cylinders 36 for pressurization. This pressurized air is then emitted from the outlet 38 of the low-pressure cylinder 36 to the inlet 40 of a middle cooler 39. The cooler 39 is installed at the underside of the base frame 30 so that it releases the heat and is effectively cooled down by the surrounding air. The air is then conveyed from the outlet 41 of the middle cooler 39 to the inlet 43 of the high-pressure cylinder 42 and is further compressed to a higher level. The compressed air from the outlets 44 is connected to a common pipe which leads to the back cooler, not shown in FIGS. 2a, 2b, and 2c.
The four suspension pieces 31 are connected, such as by welding, to the base frame 30 at their lower ends so that the base frame 30 is suspended from each of the four corners thereof. Their upper ends are fixed to the underside of the floor of the cars by suitable bolts or nuts which cooperate with vibration-proof flexible washers or rubber or neoprene dampening mounts 21.
In such an arrangement, the compressor 4 is driven by the motor 3 through the rotation of the rotating shaft 13 which movement is transferred to the crank shaft 16 by the coupling member 17. Thus, the low-pressure cylinder 36 and the high-pressure cylinder 42 are operated, and the air which is sucked in passes through the suction dust filter and the suction muffler. The air is then conducted to two low-pressure cylinders and also to two high-pressure cylinders in the direction shown by the arrows in FIG. 2c so that the air is effectively compressed.
It will be appreciated that any dust in the atmosphere is filtered by the suction dust filter 5 to prevent excessive wear to the compressor 4, and the suction sound of the compressor 4 is masked by the suction muffler 6. The vibration which comes from the compressor 4 and/or the electric motor 3 is decreased by the vibration-proof flexible washer dampeners or rubber bumpers 21.